1. Field of the Invention
The present invention relates to variable valve controllers for internal combustion engines and methods for operating the same. More particularly, the present invention relates to a variable valve controller including a first variable valve mechanism capable of changing a valve timing, and a second variable valve mechanism capable of changing a valve lift, and a method for operating the same.
2. Description of Related Art
Variable valve controllers for internal combustion engines are known in some respects. For example, Japanese Unexamined Patent Application Publication No. 2002-285871 discloses a variable valve controller for an internal combustion engine in which a control range of one of a valve timing and a valve lift is limited in accordance with a control condition of the other of the valve timing and the valve lift when the valve timing and the valve lift are to be controlled.
In particular, a target value of a valve lift of an intake valve is calculated to control the valve lift based on the target value. Also, an actual value of the valve lift is detected, and an advance limit value of a valve timing of the intake valve is set on the basis of the actual value of the valve lift, to control the valve timing so as not to exceed the advance limit value. Accordingly, the intake valve is prevented from interfering with a piston.
The variable valve controller for the internal combustion engine detects an error of a system and attempts to perform fail-safe control. However, if it is difficult to cooperatively control the valve timing and the valve lift due to the error, the valve timing may be a value exceeding the limit value before detection of the error because the detection of the error may take a long time. Hence, the intake valve may interfere with the piston before the fail-safe control is started.